An integrated circuit (IC) includes a number of electronic devices. One way in which to represent the IC is as a layout diagram (hereinafter, layout). A layout is hierarchical and is decomposed into modules which carry out higher-level functions as required by the IC's design specifications. In some circumstances, a semi-custom design (SCD) project decomposes the modules into macro cells, standard cells and custom cells.
For a given SCD project, a custom cell is designed with an arrangement that is specific to the given SCD project in order to provide (in operation) a higher-level logic function that is specific to the SCD project. By contrast, a library of standard cells is designed with no particular project in mind and includes standard cells which provide (in operation) common, lower-level logic functions. In terms of a footprint within a layout, custom cells are larger (typically much larger) than standard cells. Moreover, for a given library, all of the standard cells have at least one dimension which is the same size (typically, the size being a multiple of a library-specific fixed dimension) in order to facilitate placement of the standard cells into a layout. As such, standard cells are described as being predefined with respect to a given SCD project. Custom cells may or may not have at least one dimension that is the same size as the corresponding dimension of the standard cells.